A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Requirements of the lithographic apparatus in terms of throughput, resolution, etc. tend to be raised to higher and higher levels. However, the performance to be achieved is limited by the physical structure of chucks of the lithographic apparatus, such as the substrate (wafer) table or the support (such as the mask table). On the one hand, a stiff structure is desired so as to prevent an occurrence of resonance modes in the stage (which may limit a bandwidth), thereby allowing to achieve a high accuracy of positioning, while on the other hand a lightweight structure would be desired in order to allow fast acceleration of the stage, thereby allowing to achieve, for example, a high scanning speed and throughput.